This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. Section 119 from an application for APPARATUS AND METHOD OF MONITORING A QUEUE STATE IN AN ASYNCHRONOUS TRANSFER MODE SWITCH filed earlier in the Korean Industrial Property Office on Jun. 16, 1999 and there duly assigned Serial No. 22452/1999.
1. Field of the Invention
The present invention relates generally to an asynchronous transfer mode switching system. More particularly, the present invention relates to an apparatus and method for monitoring the queue state of an asynchronous transfer mode (ATM) switch to control the traffic of a subscriber board in non-real time.
2. Description of the Related Art
An available bit rate (ABR) service is one of the ATM service categories defined by the ATM forum. In ABR service, resource management cells allow connection end points to request higher (or lower) cell transmission rates according to the temporal needs of the application, and the source rate is controlled by establishing a minimum bandwidth through a resource management (RM) cell for which the user may expect a low cell loss ratio for the duration of connection. Thus, it is necessary to effectively calculate the available bandwidth in the ATM switching system.
However, the conventional ATM switch has drawbacks in that the algorithms for calculating the available bandwidth of a switch node for a determined time are complicated. Moreover, the conventional ATM switching system is not provided with any communication path for informing the state of an internal queue. Currently, even if the paths for informing the state of the internal queue can be provided in the conventional ATM switching system, it is not easy to implement an apparatus for informing the state of the queue existing in various paths for a connection.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide an apparatus and method for monitoring the state of a queue when the connected calls pass through the ATM switch in a subscriber board.
Another object of the present invention is to provide a queue state monitoring apparatus and method capable of rapidly and accurately detecting congestion conditions according to the traffic change of an ATM switch in a subscriber board.
Still another object of the present invention is to provide a queue state monitoring apparatus which can effectively calculate an available bandwidth in an ATM switching system to support the available bit rate (ABR) service in a subscriber board.
In order to achieve the above objects in accordance with the present invention, the difference between the present time value and the previous input time value stored in a memory per connection is inputted to a forward resource management (FRM) cell when the FRM cell is transmitted from a source end to a destination end. When the FRM cell from the source passes through an ATM switch, the difference between the present output time value and the previous output time value stored in a memory is derived to determined a switch load measurement value, which is obtained by calculating the difference between the input time value difference and the output time value difference. Then, the calculated switch load measurement value is inputted to a backward resource measurement (BRM) cell transmitted from a destination back to the ATM switch. The queue state in the ATM switch is observed through the switch load measurement value, which is inputted to the BRM cell transmitted from the destination end via the ATM switch, and accordingly, an explicit cell rate (ER) value corresponding to the queue state is calculated so that the calculated ER value can be inputted to the BRM cell to be sent to the source end.